In the prior are there are known assemblies made up of a frame and a member such as a seat or nacelle which can be separated by control of appropriate mutual fastening members. In accordance with the prior art the operating fastening members are always arranged on the frame to engage fixed members present on the reception member. Operation of these fastening members is always difficult because they are located beneath the reception member. In addition, the fastening members are usually at least two in number arranged on opposite sides of the frame. Although there are proposals of two interconnected fastening members to have centralized control, usually the use of at least two independent fastening members to provide greater safety against accidental release is preferred.
On the contrary it has been found that this introduces an additional risk factor. Indeed, whether with independent fastening members or centralized control, once the fastening members are released the reception member merely rests on the frame while the user has his hands still engaged in the releasing operation. The user must then quit both the frame and the reception member to be able to seize the reception member at the points or grips provided for that purpose. There is thus a lapse of time during which an uncontrolled movement of the child in the reception member or an involuntary external blow could cause falling of the reception member from the frame. In the prior art it was sought to eliminate the danger by providing fastening members with precise predetermined mostly horizontal release directions to be followed once appropriate stops were opened. Although this reduces the danger there is still a possibility that the accidental movement take place just in the separation direction causing separation and falling.
Another shortcoming of the above mentioned prior art is that by requiring predetermined separation movements even the mutual hooking movement which in general must mainly take place simultaneously on opposite sides of the frame becomes difficult.
In addition it is impossible to prearrange automatic hooking systems e.g. with springs since it is necessary that the fastening members have a permanent release position to allow the user to abandon them to grasp the reception member and remove it. It is therefore possible to forget to lock the reception member firmly on the frame. If it is considered that usually the hooking and unhooking operations take place with the child present in the reception member and hence with the need to lift and move the weight thereof, the difficulty of use becomes evident.